Currently, carbon-carbon composite parts are often attached to one another by mechanical means, such as rivets, or by glues. These methods are not satisfactory for carbon-carbon composite parts that are used as friction materials in aircraft brakes, due to the high loads and very high temperatures that are encountered in that environment.
U.S. Pat. No. 5,972,157, assigned on its face to AlliedSignal Inc., discloses joining together carbon-carbon composite parts by means of a reactive-bonding joint interlayer. The interlayer is formed of fine particles of carbide-forming metallic ingredients and carbon. U.S. Pat. No. 5,972,157 teaches that the reactive-bonding layers are metal-rich non-stoichiometric mixture of meals and carbon. “The metals included in the compounds may include at least one element selected from the group consisting of W, Ti, Si, Ta, Nb, Zr, Hf, V, Cr, and Mo. . . . Tungsten is the preferred major metallic ingredient in the joint compound . . . . In some cases, short carbon fibers having an average length up to 5 mm in length are incorporated into the reactive-bonding layer to further reinforce the joint . . . . The reactive-bonding layer may also contain one or more refractory compounds as filler materials . . . . Representative of such refractory compounds are TiB2, BN, B4C, SiC, TiC, MoSi2, WSi2.” Column 3, line 43—column 4, line 24. U.S. Pat. No. 5,972,157 discloses in Example 1 joining together two carbon-carbon composite parts with a bonding layer of a slurry made from 10 grams of tungsten powder and 0.5 grams of carbon powder and 12 milliliters of methanol. The joined parts with the bonding layer between them were heated in an argon atmosphere and under a compressive pressure of 5 megapascals to a temperature of 1450-1580° C. for a period of from 10-30 minutes.
In summary, the process of U.S. Pat. No. 5,972,157 requires several relatively complex steps, including: placing the pieces to be bonded into a non-oxidizing atmosphere; heating the pieces, under pressure, to the ignition point of carbon and titanium (that is, about 1600° C.); maintaining the pressure while the reaction occurs; and cooling the joined pieces to below the oxidation temperature of carbon-carbon while maintaining the non-oxidizing atmosphere.